Radial piston device with self-aligning piston assembly



July 16, 1968 J. TOBIAS RADIAL PISTON DEVICE WITH SELF-ALIGNING PISTON ASSEMBLY FIG. 2

Filed April 4, 1966 0) Q Ln INVENTOR.

JAROMIR TOBIAS ATTORNEY United States Patent 3,392,634 RADIAL PISTON DEVICE WITH SELF-ALIGNING PISTON ASSEMBLY Iaromir Tobias, Box 141, Road 2, Rhinebeck, N.Y. 12572 Continuation-impart of application Ser. No. 508,249, Nov. 17, 1965. This application Apr. 4, 1966, Ser. No. 539,861

4 Claims. (Cl. 92--58) ABSTRACT OF THE DISCLOSURE A hydraulic pump or motor of the radial free piston type wherein the pistons carried in the cylinder bores of a rotating block engage against an annular, rotatably mounted reaction ring whose axis is offset from the axis of rotation of the block, characterized by piston stabilizing connection between the reaction ring and the head of the pistons, defined by spaced-apart areas of contact between the piston and the reaction ring to either side of a plane extending through the axes of the cylinder bores, said stabilizing contact assuring that the axes of the pistons will coincide with the axes of the cylinder bores supporting the pistons, thus eliminating the need for providing a larger overlap bet-ween each piston and its cylinder bore at the radial outermost position of the piston.

This application is a continuation-in-part of my copending application Ser. No. 508,249, filed Nov. 17, 1965, now Pat. No. 3,345,916.

This invention relates to a pump or motor of the free radial piston type More particularly, this invention relates to a radial piston pump or motor of the type in which a series of pistons in a rotating block are biased outwardly into contact with a reaction ring rotatably mounted within the pump or motor housing, the reaction ring being capable of having its axis of rotation offset with respect to the axis of rotation of the block.

The invention further relates to a pump or motor of the type described wherein the outer dimensions of the pump or motor housing may be reduced in size as compared with heretofore known pumps or motors of this type of equal displacement.

In a radial acting pump or motor of the free piston type, a cylinder block having an odd number of cylinder bores, typically three or more, is enclosed within a housing. The outer ends of the pistons project from the block and bear against a reaction ring which may be either rotatably or non-rotatably mounted within the housing. Inward and outward movement of the pistons within the block is achieved by offsetting the axis of the reaction ring from the axis of rotation of the block.

In the case of a hydraulic pump, the block is forcibly rotated, the eccentricity of the reaction ring with respect to the block causing an inward and outward movement of the pistons and, hence, a pumping action, the cylinder bores being sequentially connected to input and output hydraulic pressure lines, in a manner well known.

Where the device is used as a motor, pressure is fed to the cylinder bores, causing them to extend outwardly against the reaction ring and inducing a rotary motion of the block, due to the eccentricity of the reaction ring with respect to the axis of rotation of the block.

Desirably, of course, the over-all size of a pump or motor and its consequent weight should be kept to a minimum consonant with the capacity or displacement of the pump or motor. Typically, the size of rotary piston pumps and motors heretofore known, and particularly the diameter of the housing thereof, has been quite large with regard to the capacity. I have determined that one of the causes for the relatively large diameter required is the tendency, in such pumps and motors heretofore known, for the axis of the piston to become inclined with respect to the axis of the cylinder bore in which it moves, unless a sufficient length of piston remains in the cylinder bore at the outwardmost extended position of the piston to maintain the piston in alignment with the cylinder bore. The tendency for the piston to cant in the cylinder is, as expected, particularly encountered when the unit is used as a pump, although such tendency is also experienced in motors, especially where they operate under heavy, suddenly applied, intermittent loads.

The canting tendency has thus required the use of relatively long pistons, to assure a considerable overlap between the piston and the cylinder on the outward stroke of the piston. The canting tendency is increased by the fact that normally a piston assembly does not comprise a solid cylinder mass but, rather, in accordance with known practice, a series of piston or 0 rings mounted in annular shoulders formed on the piston provide the actual contacting surfaces which support the piston in axial alignment with the cylinder bore.

The use of piston or 0 rings, with their inherently reduced stability as contrasted with solid contacting piston and cylinder surfaces, further heightens the problem so that, in accordance with present practice, a considerable length of piston must remain in the cylinder even in the outwardmost extended position of the piston.

In the light of the foregoing, it is an object of my invention to provide a novel radial piston motor or pump wherein a minimum of piston length need remain in the cylinder bore at the outwardmost extended position of the piston.

A further object of the invention is the provision of an improved radial piston motor or pump wherein the engaging surfaces of the piston head and the reaction ring function to maintain the piston in axial alignment with the cylinder bore. In view of the fact that the alignment function in the device of the invention is effected in part at the head or radial outer end of the piston, it is not necessary to maintain a considerable length of piston within the cylinder to preserve the required axial alignment. By reducing the amount of required overlap, it is possible, as will be evident from the foregoing to reduce the overall diameter of the pump or motor housing without reducing the capacity or displacement of the pump or motor.

To attain these objects and such further objects as may appear herein or be hereinafter pointed] out, I make reference to the accompanying drawings, forming a part hereof, in which:

FIGURE 1 is a discontinuous vertical section through a radial piston pump in accordance with the invention, the section being taken on the center lines of two angularly ofiset piston members;

FIGURE 2 is a magnified section taken on the line 2-2 of FIGURE 1;

FIGURE 3 is a perspective view of the head portion of a piston member in accordance with the invention.

Reference will now be made to the drawings wherein a frame 10 supports a pump or motor housing 11. A pintle shaft 12 is fixed to the housing, the shaft being hollow to define input and exhaust passages 13, 14, which passages open to the periphery of the shaft in the areas 15, 16, respectively.

A cylinder block 17 is rotatably mounted about the pintle shaft 12, the block herein illustrated being constructed in accordance with my previously mentioned copending application. The block includes a plurality of radially directed cylinder bores 18, which bores communicate by porting passages 19 with the discharge areas 15 and 16 as the block rotates about the pintle shaft. The bores 18 open outwardly at the periphery of the block 17.

A drive shaft 20 is. communicated to rotate with the block 17, it being understood that where the unit is to be used as a pump, the shaft will be rotated and then will rotate the block whereas where the device is used as a motor, the rotating block communicates its motion to the shaft 20.

Within the housing 11 there is rotatably mounted an annular reaction ring 21. The reaction ring is free to rotate with respect to the housing, a series of anti-friction rollers 22 or similar means being interposed between the ring 21 and the housing. The reaction ring, in its inwardly directed portion, is hollowed and defines a generally trough-shaped or trapezoidal conformation defined by angularly sloping side walls 23, 23, connected by a transversely extending base portion 24. As will be more fully understood from the ensuing description, it is the coaction of the inner surface of the reaction ring, and: particularly of the side walls 23, 23, with portions of the piston head next to be described, which provides the stabilizing influence at the piston head which eliminates the requirement for large overlaps between the pistons and the cylinder bores.

The pistons 25 are generally cylindrical in conformation and may include one or more piston rings, rings or the like (not shown). The outermost end 26 of the piston of the illustrated embodiment is generally square in plan, the piston including four angular panels or walls 27, 28, 29, 30, which merge with the squared end 26 thereof and taper angularly and merge with the side walls of the piston. The angle of the panel portions 27 to 30 with respect to the axis of the piston is preferably identical to the angle defined by the sides 23 of the reaction ring with respect to a plane normal to the axis of the reaction ring. The junctions between the panels 27, 28, 29 and 30 are preferably ground away or rounded, as at 31.

As best seen from FIGURE 1, when the piston 25 is outwardly biased, by one or more of the factors including centrifugal force and/or the presence of a super-charger pump in accordance with United States Patent No. 3,165,069 of Jan. 12, 1965, it will be evident that due to the interfit between a pair of opposed panels, either 27 and 29 or 28 and 30, of the piston head with the walls 23 of the reaction ring, that a stabilizing influence will be exerted by the interfitting parts on the piston, which infiuence will tend to maintain the piston axis coincident with the cylinder bore axis.

At this point it should be noted that the objectionable tendency of the piston in the usual construction to cant or to be inclined within the cylinder bore is in a direction to the right or left, as viewed in FIGURE 2, rather than to the right or left as viewed in FIGURE 1, it being known in such other devices to provide a reaction ring track which incorporates an arcuate section. In other words, the pistons, where such a track is used, will seldom tend to depart from axial alignment with a lane normal to the pintle shaft axis. The canting difliculties arise primarily from a tendency of the piston axis, although remaining in said plane, to lag or lead the cylinder bore axis.

By reason of the curvature of the reaction ring track and the flat nature of the panels 27 to 30, it will be evident that each panel, when pressed against the side portion 23 of the track, will engage against each said track at two spaced points along the panels and particularly adjacent the beveled or chamfered corners 31 thereof. Thus, there is, in essence, a two point or two area contact between the piston head and the reaction ring at each side of the piston head. Such two point contact tends to center or orient the piston in axial alignment with its cylinder, the angular contacting portions acting essentially as cams and as supports to prevent and/or immediately correct any deviation of the piston from aligned position under the influence of the radial outward force applied to the piston.

In order that the centering or aligning force be maximized, the track of the reaction ring is configurated so that the base portion 24 thereof is clear of contact with the head of the piston.

Optionally but preferably, a lubricating fluid may be disposed within the track, the fluid being retained within and distributed about the track by the centrifugal forces which result from rotation of the reaction ring.

In certain structures heretofore known, the reaction ring forms a part of, or is not free to rotate relative to, the housing. In such devices, the piston ends move relative to the reaction ring. Such a structure is not suitable for use with a device in accordance with the present invention since the friction between the pistons and the reaction ring would provide an insuperable obstacle, and it is only where the reaction ring is free to rotate that the present concept may be employed.

By reason of the cradling or centering effect aforesaid, a relatively small overlap between the piston and cylinder at the outwardmost extent of the piston stroke is permissible when using the construction of the present invention. Such a condition is shown in the interfit of the piston 25 and the cylinder bore 18 at the lowermost portion of FIGURE 1.

The small overlap will enable the overall diameter of the housing 11 to be reduced, without reducing the displacement of the device.

While I have illustrated a specific suitable interfitting configuration of piston head and reaction ring wall, it will be understood that other configurations which provide a cradling or centering action against displacement of the piston from the cylinder bore in the direction of rotation of the block and normal thereto may be found suitable. such variations, providing both sidewise stabilization and stabilization in the direction of rotation, are considered to be within the spirit of the present invention and, accordingly, the invention is to be broadly construed within the scope of the appended claims.

Thus, the cradling action of the piston and the reaction ring in accordance with my invention should be distinguished from the mere sidewise centering action which would occur if a piston with a frusto-conic end portion were forced into a reaction ring having inclined side wall portions. Specifically, such conic section would engage the reaction ring walls at a single line to each side of the piston, and While such engagement would stabilize the piston against deviations normal to the plane of rotation of the block, they would not significantly prevent deviations within said plane. Conversely, a flat ended piston acting against a reaction ring comprising a fiat annular track might provide stability in the direction of rotation, but would not provide sidewise stability. I have determined that minimum piston-cylinder overlap, with its consequent size reduction, can be achieved only where stability in both planes is assured by the engagement of the piston head and reaction ring. Such stability in turn depends on contact between the reaction ring and the piston end at spaced points on each side of said piston, whereby the inclined sides of the ring tend to center the piston in the plane of rotation and the camming co-action of the spaced engaging parts of the piston head and the reaction ring aligns the iston axis with the cylinder bore axis to prevent lag or lead in the direction of rotation.

Having thus described the invention and illustratde itS use, what is claimed as new and is desired to be secured by Letters Patent is:

1. A radial free piston motor or pump comprising a shaft, a cylinder block mounted for rotation about said shaft, said block having radial cylinder bores, a housing supporting said shaft, a reaction ring rotatably mounted within said housing about an axis of rotation parallel with and offset from the axis of rotation of said block, pistons reciprocably mounted in said cylinders, piston heads immovably fixed to said pistons and interengaging portions on said piston heads and said ring, said portions including spaced apart support surface means providing surface contact areas between said ring and piston heads at at least two angularly spaced apart areas to each side of a plane passing through said cylinder bores for maintaining the axes of said pistons coincident with the axes of said bores when said pistons are radially outwardly biased against said ring 2. A hydraulic pump or motor of the radial piston type comprising a shaft, a block mounted for rotation about said shaft and including a plurality of radially extending cylinder bores, the axes of said bores being disposed in co-planar alignment, said plane being normal to the axis of said shaft, a piston mounted in each said bore for reciprocatory movement, a housing surrounding said block, a reaction ring supported in said housing for rotation about an axis parallel to the axis of said shaft, said reaction ring and said shaft being mounted for relative lateral movement with the axes of said shaft and said ring maintained parallel, said ring including an inwardly open annular track portion, said track portion having inwardly diverging inclined side wall portions evenly spaced to the opposite sides of said plane, said pistons having immovable piston head portions thereon, each configurated with angularly spaced-apart surface areas to engage each said side wall portion at two angularly spaced-apart areas and to provide clearance between said annular track and the portions of said piston heads between said spacedapart engaging surface areas.

3. A device in accordance with claim 1 wherein said track is generally trough-shaped in transverse section, said side wall portions of said section being linear and defining the sides of said trough, the radial outermost ends of said side wall portions being joined by a portion defining the base of said trough, said base and the radial outermost ends of said pistons providing the clearance space therebetween at all positions of said pistons.

4. A device in accordance with claim 3 wherein said radial outermost end of said piston is generally square in plan.

References Cited UNITED STATES PATENTS 2,205,913 6/1940 Stacy 103161 2,457,101 12/1948 Horton 103-461 3,044,412 7/1962 Orshansky 103-161 3,087,437 4/1963 Henrichsen 103-161 3,289,604 12/1966 Wahlmark 103162 FOREIGN PATENTS 794,873 12/1935 France.

538,199 11/1931 Germany.

583,396 12/1946 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner. I. C. COHEN, Assistant Examiner. 

